Purification of naphthenic acids



Patented Feb. 23 1937 UNITED STATES PATET OFFICE rnamonrron or minimum:ACIDS Waldersee B. Hendrey, Beacon, N. Y., asslgnor to The TexasOompany, Ne w York, N. Y., a corporation of Delaware No Drawing.Application April 19, 1933, semi No. 666,844

20 Claims. (Cl. 260-108) form of their alkali metal salts. Inasmuchasthese acids find extended use in the arts, processes have been devisedfor the recovery and purification of such acids. The methods employed upto the present time however for refining, that is decolorizing saidacids, have met with little success since they all fail to reduce thecolor oi. the acids to a degree necessary to meet the requirements ofthe arts, such as for instance the grease making industry.

The object of the present invention is to provide a process of producingstable light colored naphthenic acids from vacuum lubricating stillresidues or bottoms.

In accordance with the present invention these and other objects areattained by'separating the free acids from the still bottoms or residuesand then subjecting the acids to a treatment with concentrated sulfuricacid, followed by a vacuum distillation of the naphthenic acids in astill composed of or provided with alining of a material which will notunfavorably influence the color of the acids at the distillationtemperature. -Materials which nicely satisfy this requirement arealuminum and alloys or alloy steels containing chromium, and nickel inconsiderable amount, as, for example, 18% chromium and 8% nickel.

A very peculiar feature of my process is that the acid treatment of thefree naphthenic acids unaccompanied by a subsequent vacuum distillationhas no marked improving effect upon the color of the acids. Conversely avacuum distillation without the acid treating step is not efiicacious inpermanently lowering the color of the crude naphthenic acids. Lightcolored acids can be obtained by proper distillation but the-colordarkens badly in storage. The color is only removed when the acidtreating and distillation.

steps are applied in proper sequence. The par- Y 'ticular reason whythis occurs is unknown to me.

which would otherwise become dark after distillaition. This, of course,is only a theory on my part i and hence my disclosure should not be inany way limited in view thereof.

In carrying out my invention, beginning with the crude alkaline stillbottoms obtained by redistilling vacuum lubricating distillates fromGulf Coast crude oils over caustic, it is best to first emulsify thebottoms with water and then liberate the free acids from their alkalimetal salts by the addition'of a strong mineral acid, such as sulfuricacid, according to the usual practice. The acids can then be drawn offand distilled to leave behind a large quantity of the admixed oil and lother impurities. The distilled crude acids thus obtained can then besubmitted to my refining treatment to effect a conversion thereof intowater in an emulsifying tank and heated to 150 200 F. In the event thatthe bottoms are passed 'directly into the emulsifying tank from thestill no external-heat is required since the bottoms are at atemperature of 400-600 F'. when they are drawn from the still. Theemulsified residue'is then treated with an acid of the nature ofsulfuric acid. For instance, one may use any of the ordinary strengthsof commercial sulfuric acid or even waste acid. The amount of acid usedmay vary between 6 to 12% by weight of 98% acid based on anhydrousbottoms. The actual quantity of sulfuric acid used is'dependent on thesodium naphthenate and free alkali content of the bottoms, suflicientsulfuric acid being used to neutralize any .excessalkali and to convertthe sodium naphthenate to free acid. The resultant acidified solution isthen allowed to settle to permit the free naphthenic acids to separateout. The crude free acids are then pumped oil, a.

product thus being obtained containing about 30% of water. During thesettling period the temperature is maintained preferably at 140- 200 F.

The wet acids are then run into a heated insulated tank for furthersettling in order to reduce the water content in the free naphthenicacids to as low as 540%, The temperature of the solution during thissettling operation is also maintained at about -200" F. The settling outof the water from the acid may be expedited naphthas, kerosene, and thelike. It is advisable to reduce the water content below this amount ifthe acids are to be distilled in a batch distillation.' This, however,may be done in the still by a careful regulation of the temperature, thewater being reduced to about 2% before distilling.

Considerable time is saved, however, by directly distilling the wetacids of say 5'-l0% water content in a tube still to produce a firstdistilled naphthenic acid which is relatively dark in color. During thisinitial distillation the preheater temperature is maintained atapproximately 622 F. and the stream temperature at approximately 478 F;at 29 in. mercury vacuum. A distillate is thus obtained comprising froml-4% of naphthas, -40% of naphthenic acids and from 60-74% of very heavybottoms which may be utilized for fuel or other suitable purposes. Thesaponification value of the initially distilled naphthenic acidfractions should be as high as possible (e. g. 100 up to about 270) andusually have a viscosity of about 150 Saybolt Universal at 210 F.

The once distilled naphthenic acids are then treated with sulfuric acid.Satisfactory results have been obtained by using approximately 5% byweight of 98% technical sulfuric acid. The solution thus obtained isdiluted with a limited amount of water and the sludge permitted tosettle. About 20% of water based on the weight of sulfuric acid has beenfound to give satisfactory sludge coagulation. Most of the sludge can bedrawn off from the bottom. The naphthenic acid is then drawn from thetop of this settling tank into a washing chamber where the acids arewashed with water to remove any excess mineral acid. The number ofwashes required can be greatly reduced by the early use of a dilute so-0 dium carbonate solution as a wash.

The washed naphthenic acids are then again vacuum distilled indistilling apparatus fabricated from non-ferrous material or frommaterials which are resistant to chemical action by the 5' acids.Suitable distilling equipment would comprise a still and fractionatingcolumn provided with the usual condensing and cooling coils.

The yield of the naphthenic acids in this distillation ranges from 70%to 90%, depending on 50 the type of charge and also upon the temperatureof distillation. The residue is black and may be used as fuel crackingstock or added back to crude naphthenic acids for further treatment. Thesaponification value of the naphthenic acids 5 remains practicallyunchanged by the acid treatment. The color of the naphthenic acids,however, is materially lightened. The following table is the result ofcharacteristic tests made on cuts from regular acids and from treatedand 60 distilled acids:

70 Obviously manymodifications and variations of the invention, ashereinbefore set ,forth, may

be made without} departing from the spirit and scope thereof, andtherefore'only such limitations should be imposed as are indicated inthe ap- 75 pended claims.

, 3,072,058 I v I by diluting the solution with lighter oils such Thereference to a non-ferrous stillin the appended claims includes theusual distilling apparatus, comprising a still, fractionating column.condensing and cooling means.

I clalmz' l. The process of decolorizing dark colored naphthenic acidsderived from alkaline residues obtained in the distillation of mineraloil which comprises treating said acids with concentrated sulfuric acidand vacuum distilling the so treated acids.

2. The process of decolorizing dark colored naphthenic acids derivedfrom alkaline residues obtainedin the distillation of mineral oil whichcomprises treating said acids with approximately 5% by weight of 98%technical sulfuric acid and vacuum distilling the so treated acids.

3. The process of decolorizing crude naphthenic acids which comprisestreating crude alkali naphthenates to liberate crude naphthenic acids,distilling said crude acids to produce once distilled acids, treatingsaid once distilled acids with concentrated sulfuric acid and thenvacuum distilling the so treated once distilled acids.

4. The process of producing light colored naphthenic acids from vacuumlubricating still residues which comprises treating said residues with ian acid stronger than naphthenic acids to free the naphthenic acidscontained therein, distilling the naphthenic acids thus freed to produceonce so distilled naphthenic acids, treating said once distilled acidswith sulfuric acid and then distilling the so treated once distilledacids.

5. The process of producing light colored naphthenic acids from vacuumlubricating still resi- I dues which comprises treating said residueswith a mineral acid to free the naphthenic acids contained therein,distilling. the naphthenic acids thus freed to produce once distillednaphthenic acids, treating the once distilled naphthenic acids withconcentrated sulfuric acid and then distilling the so treated oncedistilled naphthenic acids.

6. The process of producing light colored naphthenic acids from vacuumlubricating still residues which comprises treating said residues withsulfuric acid to free the naphthenic acids contained therein, vacuumdistilling the naphthenic acids thus freed to produce once distillednaphthenic acids, treating said once distilled naphthenic acids withconcentratedsulfuric acid and then vacuum distilling the so treated oncedistilled naphthenic acids in a still formed of a material which willnot unfavorably influence the color of the acids at the distillationtemperature 7. The process of producing light colored naphthenic acidsfrom vacuum lubricating still residues which comprises emulsifying saidresidues, treating said emulsified residues with a mineral acid to freethe naphthenic acids contained therein, distilling the naphthenic acidsthusfreed to produce once distilled naphthenic acids, treating said oncedistilled naphthenic acids with concentrated sulfuric acid and thendistilling the so treated once distilled naphthenic acids in a stillformed of a material which will not unfavorably influence the color ofthe acids at the distillation temperature.

8. The process of producing light colored naphthenic acids from vacuumlubricating still residues which comprises emulsifying said residueswith water, treating the resultant emulsified solution with a mineralacid to free the naphthenic acids "contained in said residues,permitting the v solution to settle to decrease the water content 7 ofsaid naphthenic acids, distilling said naphthenic acids, treating saiddistilled naphthenic acids with concentrated sulfuric acid, anddistilling the so treated naphthenic acids in a still formed of amaterial which will not 'unfavorably influence the color of the acids atthe distillation temperature.

9. The process of producing light colored naphthenic acids from vacuumlubricating still residues which comprises emulsifying the residues withwater, treating the resultant emulsified solution with a mineral acid tofree the naphthenic acids contained therein, permitting the solution tosettle to decrease the water content of said naphthenic acids,distilling the said naphthenic acids, treating said distilled naphthenicacids with concentrated sulfuric acid, diluting the resultant solutionwith water, permitting the diluted solution to settle to separate outthe naphthenic acids, washing said naphthenic acids to remove excessmineral acids therefrom, and then vacuum distilling said washed acids ina still formed of a material which will not unfavorably influence thecolor of the acids at the distillation temperature.

10. The process of producing light colored naphthenic acids from vacuumlubricating still residues which comprises emulsifying the residues withwater, treating the resultant emulsified solution with sulfuric acid tofree the naphthenic acid contained therein, permitting the solution tosettle to decrease the water content of said naphthenic acids,distilling the said naphthenic acids, treating said distilled naphthenicacids with concentrated sulfuric acid, diluting the resultant solutionwith water, permitting the solution to settle to separate out thenaphthenic acids, washing said naphthenic acid with water to removeexcess mineral acids therefrom, and then vacuum distilling said washedacids in a still formed of a material which will not unfavorablyinfluence the color of the acids at the distil lation temperature. l 11.The process of decolorizing dark-colored naphthenic acids derived fromalkaline residues obtained in the distillation of mineral oil whichcomprises preliminarily treating said residues to liberate crudenaphthenic acids, removing the liberated acids, treating said acids withconcentrated sulphuric acid, and .vacuum distilling the so treated acidsin a distilling zone the interior surface of which is formed frommaterial which will not unfavorably influence the color of the acids atthe distillation temperature.

'l2.'The process of decolorizing dark colored naphthenic acids derivedfrom alkaline residues obtained in the distillation of mineral oil,which comprises treating said acids with concentrated sulfuric acid, anddistilling the so treated acids.

13. In a process for purifying naphthenic acids contaminated withcarbonaceous materials, the steps of contacting said acids with anoxygencontaining, inorganic acid, diluting with water the mixture ofnaphthenic and oxygen-containing, inorganic acid and separating thenaphthenic acids from the resulting coagulated sludge, and distillingthe so treated acids. 1

14. In a process for purifying naphthenic acids contaminated withcarbonaceous materials, the steps of contacting said acids with anoxygencontaining, inorganic acid, diluting with water the mixture ofnaphthenic acids and the oxygencontaining, inorganic acid, separatingthe naphthenic acids from the resulting coagulated sludge, washing theseparatednaphthenic acids with a reagent adapted to remove any residualinorganic acidity therefrom, and distilling the so treated acids.

- 15. In a process for purifying naphthenic acids contaminated withcarbonaceous materials, the steps of contacting said acids. with anoxygencontaining, inorganic acid, diluting with water the mixture ofnaphthenic acids and the oxygencontaining, inorganic acid, separatingthe naphthenic acids from the resulting coagulated sludge, washing theseparated naphthenic acids with a reagent adapted to remove any residualinorganic acidity therefrom, distilling the naphthenic acids which arefree from inorganic acidity and condensing the overhead product, anddistilling the. so treated acids.

16. The process of producing decolorized naphthenic acids from alkalineresidue containing sodium naphthenates obtained in the treatment ofmineral oil, comprising preliminarily treating said residue to liberatecrude naphthenic acids, removing the liberated acids, treating saidacids with concentrated. sulphuric acid and distilling the so treatedacids.

18. The process of decolorizing dark-colored naphthenic acids derivedfrom alkaline residues obtained in the distillation of mineral oil,which comprises acid-treating said naphthenic acids with strong acid toremove carbonaceous materials therefrom in the form of a sludge, anddistillingthe so treated acids.

19. The process of decolorizing dark-colored naphthenic acids derivedfrom alkaline residues obtained in the distillation of mineral oil,which comprises acid-treating said naphthenic acids with strong acid toremove carbonaceous materials therefrom in the form of a sludge,removing the resulting sludge, neutralizing the treated naphthenic acidsto remove remaining strong acid therefrom, and distilling the so treatedacids.

20. The process of decolorizing dark-colored naphthenic acids derivedfrom alkaline residues obtained in the distillation of mineral oil,which comprises treating said acids with concentrated sulphuric acid,removing the resulting sludge, neutralizing the treated naphthenic acidsto remove sulphuric acid therefrom, and distilling the so treated acids.

WALDERSEE B. HENDREY.

